We propose to use functional magnetic resonance imaging (fMRI) to examine the frontal neural systems involved in working memory of adults with attention deficit hyperactivity disorder (ADHD). Adult ADHD is associated with functional impairments in multiple life domains and is also associated with poorer performance on tasks of neurocognitive functioning. Despite the clinical significance of this disorder, relatively little research has been conducted on adult ADHD and researchers have questioned its validity. We will use the blood oxygenation level dependent fMRI response as a measure of neural activity. We will examine: 1) the difference in neural activity in frontal areas of the brain between adults with and without ADHD during performance on a parametric variation of a working memory task, the N-back task; and 2) how differences in patterns of neural activity in frontal areas of the brain correspond to behavioral performance on the N-back task, We hypothesize that: 1) while performing the N-back task, adults with ADHD will show less neural activity than matched healthy controls in frontal areas, particularly the lateral prefrontal cortex, which is critical for working memory; and 2) behavioral performance on the N-back task will be correlated with frontal activity. We hope to further elucidate the validity of this disorder and contribute to our understanding of the neural mechanisms involved with its manifestation.